Ad conversion measurement without cookies

Google has a plan to maintain accurate performance measurements without third-party cookies. One of the cornerstones of that plan is a proposed Attribution Reporting API (previously known as Conversion Measurement).

The Attribution Reporting API aims to maintain performance measurement when a conversion happens without third-party cookies or tracking mechanisms.

The basic principle breaks away from the traditional tracking method of matching the identity of a user between a publisher’s site and an advertiser’s site. The diagram below illustrates a side-by-side view of today’s web (joined identity) and tomorrow’s web (partitioned identity), envisioned by the Google Privacy Sandbox proposal.

Google Attribution Reporting APIThis ensures privacy, although it leaves open the question of how to ensure conversion data continues to flow back to the advertiser for tracking purposes. To solve this quandary, Google suggests splitting tracking in two distinct parts:

Event-level reporting

This is information pertaining to an actual conversion event. This information is stored locally, on the users’ own device where it will remain private.

Aggregate-level reporting

These are reports that allow advertisers to know overall metrics for their campaigns – such as ROI, conversion rates etc. – but without being able to drill down to individual events. In addition to the privacy protection offered by putting people into large groups, additional noise (randomized data to blur the data’s accuracy) will also be added.

At the moment, advertisers do not need to implement any changes to their campaign tracking setup. However, advertisers will need to accept that reporting in the future will not be as detailed as it used to be. Improving first-party data collection remains the best way to ensure long-term viability of advertising strategies.

Of course, both Meta and Google have relied on data modelling techniques for a while now to “plug” the gaps in coverage from the current (limited) loss of third-party cookies. The fact that reporting on ad platforms provides a broad picture of what’s happening, rather than a detailed understanding of where conversions come from, is a concept advertisers are already familiar with.

Attribution Reporting API is part of the larger Privacy Sandbox initiative, and can be tested within Chrome’s origin trials. Google will evolve the idea over time based on results from those trials. Stay tuned for further updates. Our account managers will inform clients of any changes needed.